Interpretation of joint trends in traffic volume and traffic-related wildlife mortality: a case study from Key Largo, Florida

Certain combinations of time trends in traffic volume and traffic-related wildlife mortality can provide strong evidence for trends in the wildlife population itself. For example, if traffic volume increases over time while traffic-related wildlife mortality decreases over time, the wildlife population itself is almost certainly decreasing. From 1995 to 1999 the traffic volume on a road at the north end of Key Largo, Florida, increased steadily from 2,500 to 3,900 annual average daily traffic (AADT). Complete daily surveys of wildlife road kill over the same period, conducted by Florida State Parks employees, revealed significant declines in the numbers of both birds and herptiles killed over the same period. We argue that the combination of increasing traffic volume with decreasing road kills indicates declines in these wildlife populations. We present a general scheme for interpretation of joint trends in traffic volume and traffic-related wildlife mortality